my stock is primarily gas engine oil, with some ATF, diesel oil, gear oil, and possibly small amounts of whatever else i have around (brake fluid, solvent, etc), as until recently, all waste fluids went to the same place.

Oh. I meant to say that I would avoid brake fluid at all costs. It's corrosive and I imagine could do a real number on the insides of your injection pump, not to mention your cylinders and valves.